The presence invention relates in general to a method for the automatic coarse differentiation between a liquid or a bulk material of a filling product present in a receptacle by analyzing an echo signal, in particular by analyzing the therefrom generated envelope curve of a filling level measuring device. The present invention further relates in general to devices for the automatic coarse differentiation between a liquid or a bulk material of a filling product present in a receptacle by analyzing an echo signal, in particular by analyzing the therefrom generated envelope curve, as well as filling level measuring devices working in particular on the pulse echo principle and scanning a reflected echo signal.
Filling level measuring devices working on the pulse echo principle and scanning a reflected echo signal, generate from the scanned echo signal a series of data for each echo in the echo image or the so-called envelope curve. Generating an envelope curve from echo signals is sufficiently known and, accordingly, further explanations as to this technology are not required here (cf., for example, German Patent DE 44 07 369 C2; M. Scholnik xe2x80x9cIntroduction to Radar Systemsxe2x80x9d, 2nd edition, 1980, McGraw-Hill; Peter Devine xe2x80x9cRadar level measurementxe2x80x94the user""s guidexe2x80x9d, VEGA Controls Ltd., 2000, ISBN 0-9538920-0-X).
Conventional filling level measuring devices or sensors detect the filling level by measuring individual echoes in the envelope curve. A method for the filling level measurement according to the radar principle is described in European Patent Application EP 1 039 273 A1, by means of which a non-planar, in particular arched bottom can be determined by examining the measurement signal or the envelope curve for a typical noise signal behavior. When this typical noise signal behavior is determined, the empty state of the receptacle is detected. A characteristic feature for the noise signal behavior of the measurement signal consists in erratic random changes of the local peaks or in an increasing amplitude of the local minimum or maximum points with a rising frequency. German Patent DE 43 32 071 A1 described a method for the filling level measurement according to the radar principle is known, wherein the actual echo function is compared to memorized undisturbed echo function, which corresponds to an undisturbed measurement, and deviations ascertained in the antenna zone and the short range following the antenna, are evaluated for recognizing an initial formation and/or other disturbances. Furthermore, Great Britain Patent Application GB 2 123 237 A shows a filling level detector working with microwaves, which does not work according to the echo principle, but causes the reflected beam to interfere with a beam branched off using a waveguide.
With the conventional devices, it is, however, necessary for improving the evaluation of the envelope curve, to manually input whether the filling product to be measured is a liquid or a bulk material. Through this manual input, the type of the envelope curve measurement, and hence the determination of the filling level, is changed. Thus, if it is predetermined that the filling product is a liquid, the amplitude to be measured is placed at a predetermined amplitude before the maximum of the envelope curve with prior art. In case the operator has predetermined that the filling product is a bulk material, the beginning of the envelope curve up to the maximum is measured as the amplitude to be measured.
In summary, it has to be stated that according to prior art, an improved measurement of the individual echoes of an envelope curve of an echo signal depending on the type of filling product, is only then possible when a coarse manual differentiation on the filling level measuring device is carried out by an operator.
The present invention relates to a method and a device for carrying out an automatic coarse differentiation between a liquid or a bulk material of a filling product present in a receptacle. A possibility is therewith supposed to be created that a filling level measuring device working in particular on the pulse echo principle and scanning a reflected echo signal, automatically carries out a coarse differentiation between a liquid or a bulk material of the filling product.
In particular, according to a first exemplary embodiment of the present invention, a method for the coarse differentiation between a liquid and a bulk material of a filling product present in a receptacle is described, where a filling level measuring device is used scanning a reflected echo signal, and the coarse differentiation is made in dependence on the width of the individual echoes of an envelope curve in an echo signal.
According to a further exemplary embodiment of the present invention, a method for the coarse differentiation between a liquid and a bulk material of a filling product present in a receptacle using a filling level measuring device scanning an echo signal is described, where the coarse differentiation is made in dependence on the number of equidistant echoes in an echo signal.
According to yet another exemplary embodiment of the present invention, a method for the coarse differentiation between a liquid and a bulk material of a filling product present in a receptacle, using a filling level measuring device scanning an echo signal, is described, where the coarse differentiation is made in dependence on the detection of a stirring apparatus.
A preferred exemplary embodiment of a device according to the present invention for the coarse differentiation between a liquid and a bulk material of a filling product present in a receptacle, includes an arrangement for detecting the echo widths of echoes of a generated envelope curve, an arrangement for detecting the number of echoes having an echo width larger than a reference echo width, and the number of echoes having an echo width smaller than the reference echo width, and a signal outputting arrangement for the type of filling product, which signal outputting arrangement outputs a signal representative of a liquid when the number of echoes having an echo width larger than a reference echo width is greater than the number of echoes having an echo width smaller than a reference echo width.
A further preferred exemplary embodiment of a device according to the present invention for the coarse differentiation between a liquid and a bulk material of a filling product present in a receptacle, includes an arrangement for determining the number of equidistant echoes of a generated envelope curve, and an arrangement for outputting a signal determining the type of filling product in dependence on the determined number of equidistant echoes.
Still another preferred exemplary embodiment of a device according to the present invention for the coarse differentiation between a liquid and a bulk material of a filling product present in a receptacle, includes an arrangement for detecting a stirring apparatus by evaluating the echoes of a generated envelope curve, and an arrangement for outputting a signal representative of the type of filling product in dependence on the detection of a stirring apparatus.
Furthermore, according to yet another exemplary embodiment of the present invention, a filling level measuring device is described. The filling level measuring device utilizes a pulse echo principle which evaluates an envelope curve generated from the reflected echo signal, and including a device according to the above configurations. The device may also be modified according to one or more of the following configurations.
As indicated above, the present invention utilizes an idea of examining for the first time the individual echoes of an envelope curve for determined characteristics providing at least an indication as to the type of the filling product, namely liquid or bulk material. Thus, it is possible to make this coarse differentiation in dependence on the width of the individual signals of an envelope curve in an echo signal. Profit is thereby taken from the fact that, caused by the shape of a bulk material, wide echoes are more likely to occur in a product. When the filling product is a liquid, narrow echoes are more likely to occur in the envelope curve. By therewith relating the echo width of all echoes within an echo curve, or the echo image, to a predetermined reference echo width value, which is easy to fix by simple tests, then it can be concluded, if it is stated that the number of the wide echoes is larger than the number of the narrow echoes, that the filling product in question is a bulk material. Otherwise, it would be a liquid. Under circumstances, it is also purposeful to indicate that a mixture of these two basic types of filling products is concerned.
As an alternative hereto, it is yet also possible to examine the envelope curve for the fact how the distance between the individual echoes to be detected is relative to each other. Here, profit is taken from the effect that in case the filling product in question is a liquid, the echoes are more likely to occur at regular distances relative to each other. Hence, if it is stated that the echoes are present in the echo signal at regular distances, then it is possible to draw conclusions as to the type of the filling product. As an example, the case shall be mentioned that more than three equidistant echoes are detected. In this case, it is outputted that the filling product in question is a liquid.
A further alternative could consist in carrying out the coarse differentiation in dependence on the detection of a stirring apparatus. If a stirrer is recognized in the echo signal, then it may be concluded that the filling product concerned is a liquid.
It is of course also possible to combine one or more of the aforementioned alternatives for the coarse differentiation between a liquid or bulk material of the filling product, so as to increase the safety of recognizing the type of filling product. Further, it is of course also possible to lend weight to these separate alternatives with respect to each other, when they are combined, that is, to multiply them in each case with a predetermined (under circumstances even variable) factor. As a matter of course, these factors may be identical for any of the type of coarse differentiation described above, or may even be different. Through the corresponding weighting, the one or the other presented type of coarse differentiation may be imparted more or less weight.
The type of the coarse differentiation in dependence on the width of the individual echoes of an envelope curve can in particular be met in that the number of the echoes having a width larger than a reference echo width, and the number of the echoes having a width smaller than the reference echo width is ascertained. For the coarse differentiation, the ascertained larger echo number will then be referred to. Thus, as an example shall be mentioned here that in an envelope curve, four echoes are ascertained, which are larger than a reference echo width, and two echoes, which are smaller than the reference echo width. Then the coarse differentiation is made in that a bulk material is presumably concerned, since it is rather characteristic for a bulk material that the width of the echoes is larger than with a liquid.
An advantageous embodiment of this method hence provides that after the detection of the individual signals in the echo signal, the widths of individual echoes in an echo signal of an envelope curve are then ascertained by conventional (mathematical) means. Thereupon, the number of the echoes having a width greater than or equal to a reference echo width is ascertained. The number of the echoes having a width smaller than a reference echo width is likewise assessed. Thereupon, a signal determining the type of filling product is outputted in dependence on the echo widths, the number of which has been ascertained to be larger.
With the alternative for the coarse differentiation between bulk material or liquid of the filling product, wherein the equidistant echoes are ascertained in an echo signal, the distance between adjacent echoes in an envelope curve are in each case measured. Then, all echoes are preferably summarized which exhibit a distance relative to each other falling into a predetermined tolerance band (i.e. a distance range), hence equidistant echoes. The distance of the echoes is preferably calculated so that the respective locations of the maximum points of the individual echoes are determined, and the distance between these maximum points is measured. The tolerance band can be a fixed value range, e.g. xc2x10.1 m. It is in particular advantageous to take the first distance between the zero point and the first echo as the reference distance. In this case, it is for example advantageous to fix the tolerance range at xc2x150 cm, i.e. that all those echoes are considered to be equidistant echoes, the distance from each other is equal to the reference distance of xc2x150 cm. If another echo distance is fixed as the reference distance, then the tolerance band preferably has to be set to be smaller than xc2x150 cm.
In the further alternative for the coarse differentiation made with consideration of the ascertainment of a stirrer, echoes of an actual envelope curve are preferably compared with the corresponding echoes of the preceding envelope curve. Echoes from running stirrers are characterized in that their amplitude highly fluctuates, or that echoes having a large signal noise distance, i.e. the amplitude of the echo above the system noise or the dying-out transmission signal, periodically disappear and reappear. Such echoes can be marked and excluded from the filling level decision. In the present case, they are preferably used for a stirrer recognition and for accordingly outputting that the filling product in question is a liquid. Two envelope curves are in particular compared for determining the amplitude fluctuation of individual echoes, and the amplitude fluctuation thereof is compared to a reference value.
As explained above, the separate types of coarse differentiation as described before may be used individually or may be arbitrarily combined with each other. In this case, it is advantageous that the information of each type of filling product coarse differentiation is multiplied by a weighting factor, and the therefrom resulting values are added and divided by the sum of the weighting factors so as to ascertain a probability whether a liquid or a bulk material is concerned. In particular, it is then advantageous that the therefrom resulting value is compared to a reference value. If the ascertained value is, for example, smaller than this reference value, then a signal has to be outputted which is representative of liquid. In the other case, a signal has to be outputted which is representative of bulk material.
A corresponding device for the differentiation between a liquid or a bulk material of a filling product present in a receptacle, includes in an embodiment an arrangement for detecting the echo widths of echoes of a generated envelope curve, an arrangement for detecting the number of echoes having a width greater than a reference echo width, and the number of echoes having an echo width smaller than the reference echo width. Further, a signal outputting arrangement for the type of filling product is present, which outputs a signal representative of a liquid, when the number of echoes having an echo width larger than a reference echo width is greater than the number of echoes having an echo width smaller than a reference echo width.
An alternative exemplary embodiment according to the present invention includes an arrangement for detecting the number of equidistant echoes of a generated envelope curve, and an arrangement for outputting a signal determining the type of filling product in dependence on the detected number of equidistant echoes.
A further alternative exemplary embodiment of a device for the coarse differentiation between a liquid and a bulk material of a filling product present in a receptacle, is equipped with an arrangement for detecting a stirring apparatus by evaluating the echoes of a generated envelope curve, and an arrangement for outputting a signal representative of the type of filling product in dependence on the detection of a stirring apparatus.
A further preferred exemplary embodiment of the present invention may include one or more of the aforementioned arrangements, so that the different types of coarse differentiation are combined with each other. The individual arrangement work according to the above-described methods.
Finally, it has to be noted that the aforementioned methods can, for example, be implemented in an evaluation program for evaluating generated envelope curves.
Such evaluation programs are, for example, known under the trademark Echofox(copyright) of the company VEGA Grieshaber KG, Germany. Accordingly, methods and devices according to the present invention, or the correspondingly functioning software, can either be implemented in separate evaluation arrangement or, if desired, can be directly integrated in filling level measuring devices. Filling level measuring devices of the type interesting here, for the remainder, are all known filling level measuring devices, which scan a reflected echo signal, i.e. which generate en envelope curve. Such filling level measuring devices are, for example, ultrasonic filling level measuring devices or radar filling level measuring devices, in particular, so-called pulse radar filling level measuring devices.